芳香烃菲与基因碱基的非共价结合及驱动机制

Non-covalent binding characteristics of aromatic phenanthrene with genetic bases and its driving mechanisms

疏水芳香烃类化合物能够导致基因遗传性的变化,理解这些化合物对基因污染的前提是必须首先阐明污染物-基因碱基间相互作用及驱动机制.使用等温吸附-光纤固相萃取和定量-构效关系的方法,研究了模型化合物菲与4种基因碱基间的弱相互作用,并揭示了分子驱动机制.结果表明,p H=7.0条件下,腺嘌呤与菲间引力较弱;而鸟嘌呤、胞嘧啶和胸腺嘧啶对菲为分配吸附,引力较强.红外光谱和弱力等值面的分析表明,鸟嘌呤与腺嘌呤分子能够通过2组CN环(CN6环和5环)与菲的2个相互毗邻的苯核同时发生π-π引力作用;而胞嘧啶和胸腺嘧啶仅与菲弧角位置的碳原子通过电子"赠体-受体"发生静电引力作用.当环境体系变成酸性时,腺嘌呤对菲的吸附增强(分配,1/n=1),但胸腺嘧啶对菲的吸附变弱;碱性条件下,由于胞嘧啶和胸腺嘧啶存在羰基取代基,作为电子赠体的含氧嘧啶脱质子化,表面负电性增强,分子平面极化减弱,π电子更易于与菲弧角位的碳原子发生电子"赠体-受体"作用.能量计算的结果表明,对基因碱基作用位点的预测结果可信,属于自发的非共价成因的物理结合.该研究将为深入揭示芳香烃的基因污染提供理论基础,对于防治芳香烃污染、保障生态安全有重要意义.

Physical interaction between hydrophobic aromatic pollutants and genetic bases can result in changes in genetic property.It is necessary to elucidate such interaction and its driving mechanisms so as to understand the gene pollution characteristics of the aromatics.In the present study,a fiberbased solid-phase extraction experiment was conducted with a quantitative structure-activity relationship（QSAR） to investigate the weak interaction between model phenanthrene and genetic bases and to further illustrate the driving mechanisms based on the various molecular attractions.Results showed that attraction between adenine and phenanthrene is weak at pH = 7.0,while guanine,cytosine,and thymine were associated with partitioning adsorption（1/n = 1.0） and strong attraction.FTIR and computational chemistry analyses show that six-and five-membered rings of CN in adenine and guanine can collectively combine with a pair of adjacent aromatic nucleus through called π-π interaction.Combination of inscribed carbon atom in phenanthrene with six-membered ring of CN in cytosine/thymine bases relies on their electrostatic attraction between positive and negative charges.Acidic condition（pH =5.0） increases electro negativity and decreases molecular polarization of planar pyridine ring.Deprotonation of substituted oxygen groups in pyridine favors the association of π electrons in pyridine with inscribed carbon atom in phenanthrene via an ＂ electron donor-acceptor＂ attraction.Energies calculated by a batch experiment and computational chemistry show that binding sites in genetic bases are reasonable,and these interactions are attributed to a spontaneous physical process.